Computed tomography (CT), sometimes called computed axial tomography (CAT) or CAT scan, and volume computed tomography (VCT), use special x-ray equipment to obtain image data from different angles around a person's body, and then use computer processing of the data to create a two-dimensional cross-sectional image (i.e., slice) or three-dimensional image of the body tissues and organs that were scanned. CT and VCT imaging are particularly useful because they can show a combination of several different types of tissue (i.e., heart, lungs, stomach, colon, kidneys, liver, bone, blood vessels, muscles, etc.) with high spatial resolution and a great deal of clarity and contrast. Radiologists can interpret CT and VCT images to diagnose various injuries and illnesses, such as cardiovascular disease, trauma, cancer, and musculoskeletal disorders. CT and VCT images can also be used to aid in minimally invasive surgeries, and to allow for accurate planning and pinpointing of tumors for radiation treatment, among other things.
CT and VCT imaging allow structures within a body to be identified and delineated without superimposing other structures on the images created thereby. In a typical conventional CT or VCT imaging system, an x-ray source emits a fan-shaped x-ray beam that is collimated to lie within an X-Y plane of a Cartesian coordinate system, generally referred to as the “imaging plane.” The x-ray beam passes through a section of the object being imaged, typically a patient. After passing through the object and being attenuated thereby, the x-ray beam impinges upon an array of radiation detector elements. The intensity of the attenuated x-ray beam radiation that is received by each detector element varies since different parts of the body absorb and attenuate the x-rays differently. Each detector element in the array produces a separate electrical signal that is a measurement of the x-ray beam's attenuation at each detector element. The attenuation measurements from all the detector elements are acquired separately, and are then combined to produce an image transmission profile.
Currently, x-ray sources for CT and VCT are limited to fairly narrow “slices” for each revolution of the gantry because of the well-understood “cone-beam artifact” problem, in which the “edges” of the cone-like x-ray beam that emerges from a point source cannot produce enough attenuation data, thereby resulting in portions of the imaged object not being imaged at all. It would be desirable, particularly for VCT, to have an extended or “linear” x-ray source to eliminate or minimize the cone-beam artifact problem. That would make it possible to obtain CT or VCT scans that cover an entire organ in a single scan or revolution of the gantry. For example, while existing CT and VCT imaging systems and methods allow multi-slice images, having a total thickness of about 10–40 mm, to be obtained in a single gantry rotation, it would be desirable to have CT and VCT imaging systems and methods that allowed multi-slice images having a total thickness as thick as 80–160 mm or thicker to be obtained in a single gantry rotation. However, improved CT and VCT imaging systems and methods are needed in order for thicker multi-slice images to be realized.
Since existing CT and VCT imaging systems and methods have many drawbacks, it would be desirable to have improved CT and VCT imaging systems and methods that lack such restrictions. This invention provides a single, near-linear, multi-spot x-ray source that utilizes multiple x-ray targets having varying focal spots thereon so as to improve the imaging data around the edges of the object being imaged, thereby allowing thicker multi-slice images to be obtained than currently possible.